Article Question

[vcolts]

Let's say the context is that new keys will be given out for a building (change of keys). And a person is authorizing another person to pick up the key on his behalf by writing a letter.

The format would be: I, Peter, authorize John to pick up the new keys on my behalf...

Q: Is putting the definite article there grammatically correct? (I think it is the case.). If it's also okay without the definite article, then what is the reasoning for putting one there? I am naturally inclined to put "the" in there (almost feels necessary) because we are not talking about any new keys but new keys that will be given out to the tenants on a particular day.

Thanks in advance.

[Raymott]

Let's say the context is that new keys will be given out for a building (change of keys). And a person is authorizing another person to pick up the key on his behalf by writing a letter.

The format would be: I, Peter, authorize John to pick up the new keys on my behalf...

Q: Is putting the definite article there grammatically correct? (I think it is the case.). If it's also okay without the definite article, then what is the reasoning for putting one there? I am naturally inclined to put "the" in there (almost feels necessary) because we are not talking about any new keys but new keys that will be given out to the tenants on a particular day.

Thanks in advance.

You need "the". Peter is not authorizing John to pick up just any new keys that may be on offer. They are specific keys.
However, if the locks were going to be changed frequently, and Peter wants to authorise John to pick them up regularly, you could dispense with "the", and the meaning would be "any relevant keys, from now until further notice".